“Birds have evolved from reptiles.” Give palaentogical evidence in favour of this statement.

"Mammals and birds have evolved from reptiles." In what way does a comparative study of their embryology establish the validity of this statement?

Bryophytes have probably evolved from

"Pranay suffered from measles at the age of 10 years. There are rare chances of his getting infected with the same disease for the rest of his life." Give reasons for the statement

Trophical regions are likely to have more biological diversity than temperate ones. Give two reasons to justify the statement.

The statements given below describe certain features that are observed in the pistil of flowers. Pistil may have many carpels Each carpel may have more than one ovule. Each carpel has only one ovule. Pistil have only one carpel. Choose the statements that are true from options

Many discoveries in science have been accidental. This is true for plant hormones also. Can you justify this statement by giving an example? Also what term is used for such accidental findings?

ADDITIONAL QUESTIONS : The diagram below shows a germinating pollen grain and a mature ovule from an insect-pollinated flower. Some parts have been labelled. Give the letter of the nucleus which fuses with a male nucleus to form each of the following : (i) The zygote (ii) The endosperm

The existence of negatively charged particle in an atom was shown by J.J. Thomson as a result of the studies of the passage of electricity through gases at extremely low pressure known as discharge tube experiments. When a high voltage of the order of 10,000 volts or more was impressed across the electrodes, some sort of invisible rays moved from the negative electrode to the positive electrode these rays are called as cathode rays. Cathode rays travel in straight path in absence of electrical and magnetic field . Cathode rays consist of material part and charged particles? Cathode rays produce X-rays and light is emitted when they strike on ZnS screen. Cathode rays penetrate through thin sheets of aluminium and other metals . They affect the photogenic plate and passes heating effect when they strike on metal foil. The raito of charge to mass i.e charge/mass is same for all the cathode rays irrespective of the gas used in the tube. The existence of positively charged particle in an atom was shown be E. Goldstein. He repeated the same discharge tube experiments by using a perforated cathode. It was observed that when a high potential difference was applied between the electrodes, not only cathode rays were produced but also a new type of rays were produced simultaneoulsy from anode moving towards cathode and passes through the holes or canal of the cathode. These termed as canal rays or anode rays. These rays travel in straight lines and consists of positively charged particles. These rays have kinetic energy and produces heating effect also. The e/m ratio of these rays is smaller than that of electrons. Unlike cathode rays, their e/m value is dependent upon the nature of the gas taken in the tube. These rays produced flashes of light on ZnS screen and can pass throughs thin metal foils. They can produce physical and chemical changes and are capable to produce ionisation in gases. Select the incorrect statement.

Give one or two-word terms for the following statements: The plants which have stems modified for photosynthesis and leaves modified ijnto spines for protection.

These questions consist of two statements each,printed as Assertion and Reason.While asnwering these questions you are required to chose any one of the following four responses. If both Assertion and Reason are true and Reason in correct explanation of Assertion. If both assertion and Reason are true but reason is not correct explanation of Assertion. If Assertion is true but Reason is false. If both Assertion and Reason are false. Assertion:Pigeons and kites can fly for long period without undergoing fatigue. Reason:These birds have white muscle fibres which undergo slow and sustained contraction for long period.